From e72c1ccfd449598f7eda10d3bb7441d501ddcfc3 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Mon, 11 Dec 2023 09:41:31 -0800 Subject: selftests/bpf: validate eliminated global subprog is not freplaceable Add selftest that establishes dead code-eliminated valid global subprog (global_dead) and makes sure that it's not possible to freplace it, as it's effectively not there. This test will fail with unexpected success before 2afae08c9dcb ("bpf: Validate global subprogs lazily"). v2->v3: - add missing err assignment (Alan); - undo unnecessary signature changes in verifier_global_subprogs.c (Eduard); v1->v2: - don't rely on assembly output in verifier log, which changes between compiler versions (CI). Acked-by: Eduard Zingerman Reviewed-by: Alan Maguire Suggested-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko Acked-by: John Fastabend Link: https://lore.kernel.org/r/20231211174131.2324306-1-andrii@kernel.org Signed-off-by: Alexei Starovoitov --- .../selftests/bpf/progs/verifier_global_subprogs.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) (limited to 'tools/testing/selftests/bpf/progs/verifier_global_subprogs.c') diff --git a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c index a0a5efd1caa1..bd696a431244 100644 --- a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c +++ b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c @@ -10,6 +10,7 @@ int arr[1]; int unkn_idx; +const volatile bool call_dead_subprog = false; __noinline long global_bad(void) { @@ -31,23 +32,31 @@ __noinline long global_calls_good_only(void) return global_good(); } +__noinline long global_dead(void) +{ + return arr[0] * 2; +} + SEC("?raw_tp") __success __log_level(2) /* main prog is validated completely first */ __msg("('global_calls_good_only') is global and assumed valid.") -__msg("1: (95) exit") /* eventually global_good() is transitively validated as well */ __msg("Validating global_good() func") __msg("('global_good') is safe for any args that match its prototype") int chained_global_func_calls_success(void) { - return global_calls_good_only(); + int sum = 0; + + if (call_dead_subprog) + sum += global_dead(); + return global_calls_good_only() + sum; } SEC("?raw_tp") __failure __log_level(2) /* main prog validated successfully first */ -__msg("1: (95) exit") +__msg("('global_calls_bad') is global and assumed valid.") /* eventually we validate global_bad() and fail */ __msg("Validating global_bad() func") __msg("math between map_value pointer and register") /* BOOM */ -- cgit